I'm very impressed by the Nations solo tracks myself. Some very good endurance (multilap) tracks are to be found and the new blocks are beautiful!
As for the graphical updates of old environnements, they are not as big as I thought but they are welcome.

Not that anyone is going to read this because it's so deep in the thread -- but make sure you undo any mods you put on United. When I put in Rally Toon for my kids, I failed to backup the originals... Rally looks the same to me... as does desert/speed... as does Snow because I put mods on all three and they somehow transfered to the TMUnitedForever folder...